--- 2017 cash burn expected to be in the lower half of guidance range -

--- Conference call today at 4:30 p.m. Eastern Time -

Juno Therapeutics, Inc. (JUNO ), a biopharmaceutical company
developing innovative cellular immunotherapies for the treatment of
cancer, today reported financial results and business highlights for the
third quarter 2017.

"We are pleased with the potential best-in-class profile for JCAR017,
and we look forward to presenting an updated dataset at the upcoming ASH
conference," said Hans Bishop, Junos President and Chief Executive
Officer. "The clinical data continue to support our belief that a
defined cell product can improve patient outcomes. Our broad clinical
development programs and ongoing infrastructure and manufacturing
investments remain a key part of our strategy to deliver on the
potential of CAR T cell therapies for cancer patients across a broad
array of diseases."

Third Quarter 2017 and Recent Corporate Highlights

Clinical Update:

--
Juno and its collaborators will present 15 abstracts at the upcoming
American Society of Hematology Annual Meeting (ASH) and seven
abstracts at the upcoming Society for the Immunotherapy of Cancer
(SITC) meetings.

--
Presentations at ASH will include data from the ongoing Phase I
TRANSCEND study in patients with relapsed or refractory (r/r)
aggressive B-cell NHL who were treated with
fludarabine/cyclophosphamide lymphodepletion and JCAR017. New data
will be available at multiple presentations, including an oral
presentation on Monday, December 11 that will include information on
safety and responses. JCAR017 is a defined composition CD19-directed
CAR T cell product candidate using a 4-1BB costimulatory domain. Juno
believes JCAR017s clinical profile could enable outpatient
administration. The primary TRANSCEND abstract included the following
data:
--
The core group (N=49) includes patients that represent the
population that Juno is studying in the ongoing pivotal cohort.
The core group includes patients with DLBCL (NOS and transformed
from follicular lymphoma) that are ECOG Performance Status 0-1.
Topline data from the abstract for both dose levels for the core
group as of a data cutoff date of July 7, 2017 included:

--
Across both doses in the core group, the best overall response was
84% (41/49) and the best overall CR rate was 61% (30/49).

--
There was no increase in cytokine release syndrome (CRS) and
neurotoxicity (NT) rates associated with the higher dose or
between the full and core groups. Across doses in the full group,
1% (1/69) experienced severe CRS and 14% (10/69) experienced
severe NT. 30% (21/69) had any grade CRS and 20% (14/69) had any
grade NT. 64% (44/69) had no CRS or NT.

--
The most common treatment-emergent adverse events other than CRS
and NT that occurred at greater-than or equal to25% in the full group included
neutropenia (41%), fatigue (30%), thrombocytopenia (30%), and
anemia (26%).

--
Ongoing enrollment for the pivotal cohort of the TRANSCEND trial at
DL2 with BLA filing expected to be completed in the second half of
2018 and with approval as early as 2018.

--
Announced the Regenerative Medicine Advanced Therapy (RMAT)
designation for investigational drug JCAR017 for the treatment of r/r
aggressive large B cell NHL, including DLBCL, not otherwise
specified (de novo or transformed from indolent lymphoma), primary
mediastinal B Cell lymphoma or Grade 3B follicular lymphoma. Similar
to breakthrough designation, the pathway enables companies developing
cell and tissue based therapies to have earlier and more frequent
interactions with the FDA and includes opportunities for accelerated
approval, priority review, rolling submissions, and alternative
provisions to fulfill post-approval requirements under accelerated
approval.

--
Initiated a clinical trial conducted by the Fred Hutchinson Cancer
Research Center to evaluate a CAR T, FCARH143, with a fully-human BCMA
binder that preferentially binds membrane-bound BCMA. Juno intends
to begin a Phase I trial early next year using this binder in
combination with Junos cell manufacturing process. This product
candidate, JCARH125, recently received orphan drug designation from
the FDA for multiple myeloma.

Corporate News:

--
Closed a follow-on public offering and concurrent private placement
in September of 7,773,327 shares of Junos common stock at a price
of $41.00 per share. This includes the exercise in full by the
underwriters of their option to purchase up to an additional 915,000
shares of common stock and a private placement of 758,327 shares of
common stock to a subsidiary of Celgene Corporation. Gross proceeds
were approximately $318.7 million.

Third Quarter 2017 Financial Results

--
Cash Position: Cash, cash equivalents, and marketable
securities as of September 30, 2017 were $1.06 billion compared to
$801.8 million as of June 30, 2017, and $922.3 million as of
December 31, 2016.

--
Cash Used in Operating Activities and Capital Expenditures: For
the third quarter of 2017 cash used in operating activities was $40.3
million and cash used for capital expenditures was $13.9 million,
compared to cash used in operating activities of $68.1 million and
$6.4 million used for capital expenditures for the same period in 2016.

--
Cash Burn: Cash burn, which is cash used in operating
activities and capital expenditures, excluding cash inflows and
outflows from upfront payments related to business development
activities, was $54.2 million in the third quarter of 2017, of which
$59.1 million was operating cash burn and $4.9 million was net cash
provided by a tenant improvement allowance offset by capital
expenditures. For purposes of comparing the operating cash burn and
cash burn for capital expenditures for the third quarter of 2017 to
the Companys financial guidance, a cash inflow of $18.8 million for a
tenant improvement allowance was reclassified from operating
activities to capital expenditures. Cash burn in the third
quarter of 2016 was $59.5 million, of which $53.1 million was
operating cash burn and $6.4 million was cash burn for capital
expenditures.

--
Revenue: Revenue for the three and nine months ended September
30, 2017 was $44.8 million and $85.4 million, compared to $20.8
million and $58.2 million for the three and nine months ended
September 30, 2016, respectively. Revenue increased in the three and
nine months ended September 30, 2017 compared to the prior year
periods due to milestone revenue recognized in the third quarter of
2017 in connection with the Novartis sublicense agreement.
Additionally, revenue recognized under our Celgene Collaboration
Agreement and Celgene CD19 License increased in the nine months ended
September 30, 2017 compared to the prior year period.

--
R&D Expenses: Research and development expenses for the
three and nine months ended September 30, 2017, inclusive of non-cash
expenses and computed in accordance with GAAP, were $140.3 million and
$324.3 million, compared to $60.9 million and $206.9 million for the
three and nine months ended September 30, 2016, respectively. The
increases in 2017 compared to 2016 were primarily due to increased
costs to manufacture Junos product candidates, execute on Junos
clinical development strategy, expand its overall research and
development capabilities, an increase in expense related to its
success payment and contingent consideration obligations, expense
incurred for the amortization of the intangible asset associated with
the AbVitro, Inc. (AbVitro) acquisition, and an increase in non-cash
stock-based compensation expense. These increases were offset by a
decrease in milestone expense.

--
Non-GAAP R&D Expenses: Non-GAAP research and development
expenses for the three and nine months ended September 30, 2017 were
$98.4 million and $250.6 million, and include $10.6 million and $30.3
million of stock-based compensation expense, respectively. Non-GAAP
research and development expenses for the three and nine months ended
September 30, 2016 were $62.2 million and $214.5 million, and include
$7.9 million and $25.8 million of stock-based compensation expense,
respectively. Non-GAAP research and development expenses for 2017
exclude the following:
--
An expense of $37.2 million and $61.8 million for the three and
nine months ended September 30, 2017, respectively, associated
with the change in the estimated fair value and elapsed service
period for Junos potential success payment liabilities to Fred
Hutchinson Cancer Research Center (FHCRC) and Memorial Sloan
Kettering Cancer Center (MSK).

--
Non-cash stock-based compensation expense of $1.4 million and $3.0
million for the three and nine months ended September 30, 2017,
respectively, related to a 2013 restricted stock award to a
co-founding director that became a consultant upon his departure
from Junos board of directors in 2014.

--
An expense of $2.4 million and $4.8 million for the three and nine
months ended September 30, 2017, respectively, associated with
amortization of the intangible asset recorded in connection with
the AbVitro acquisition.

--
An expense of $0.8 million and $4.0 million for the three and nine
months ended September 30, 2017, respectively, associated with the
change in the estimated fair value of the contingent consideration
liabilities recorded in connection with the Stage and X-Body
acquisitions.

--
G&A Expenses: General and administrative expenses on a GAAP
basis for the three and nine months ended September 30, 2017 were
$26.3 million and $70.7 million, respectively, compared to $18.4
million and $51.2 million for the same periods in 2016. The increases
in 2017 compared to 2016 were primarily due to an increase in
consulting and other expenses to support the growing organization
including costs related to commercial readiness, increased personnel
expenses primarily related to increased headcount to support the
business, an increase in litigation and patent legal costs, and an
increase in stock-based non-cash compensation expense. The increases
in the nine month period were partially offset by decreased business
development expenses. General and administrative expenses include $6.9
million and $19.9 million of non-cash stock-based compensation expense
for the three and nine months ended September 30, 2017, compared to
$5.4 million and $15.9 million for the three and nine months ended
September 30, 2016, respectively.

--
GAAP Net Loss: Net loss for the three and nine months ended
September 30, 2017 was $118.1 million, or $1.12 per share, and $301.1
million, or $2.88 per share, compared to $56.9 million, or $0.56 per
share and $192.8 million, or $1.91 per share, for the three and nine
months ended September 30, 2016, respectively.

--
Non-GAAP Net Loss: Non-GAAP net loss, which incorporates the
non-GAAP R&D expense, for the three and nine months ended September
30, 2017 was $76.3 million, or $0.73 per share, and $227.4 million, or
$2.17 per share, compared to $58.3 million, or $0.57 per share, and
$200.4 million, or $1.99 per share for the three and nine months ended
September 30, 2016, respectively.

Juno expects to be in the lower half of 2017 cash burn guidance, which
is cash used in operating activities and capital expenditures, excluding
cash inflows or outflows from upfront payments related to business
development activities, of between $270 million and $300 million.

Conference Call Information

Juno will host a conference call today to review Junos financial
results for the third quarter 2017 beginning at 1:30 p.m. Pacific Time
(PT) / 4:30 p.m. Eastern Time (ET). Analysts and investors can
participate in the conference call by dialing (855) 780-7198 for
domestic callers and (631) 485-4870 for international callers, using the
conference ID# 2899809.

The webcast can be accessed live on the Investor Relations page of
Junos website, www.JunoTherapeutics.com,
and will be available for replay for 30 days following the call.

About Juno

Juno Therapeutics is building a fully integrated biopharmaceutical
company focused on developing innovative cellular immunotherapies for
the treatment of cancer. Founded on the vision that the use of human
cells as therapeutic entities will drive one of the next important
phases in medicine, Juno is developing cell-based cancer immunotherapies
based on chimeric antigen receptor and high-affinity T cell receptor
technologies to genetically engineer T cells to recognize and kill
cancer. Juno is developing multiple cell-based product candidates to
treat a variety of B-cell malignancies as well as multiple solid tumors
and multiple myeloma. Several product candidates have shown compelling
clinical responses in clinical trials in refractory leukemia and
lymphoma conducted to date. Junos long-term aim is to leverage its
cell-based platform to develop new product candidates that address a
broader range of cancers and human diseases. Juno brings together
innovative technologies from some of the worlds leading research
institutions, including the Fred Hutchinson Cancer Research
Center, Memorial Sloan Kettering Cancer Center, Seattle Childrens
Research Institute (SCRI), the University of California, San Francisco,
and The National Cancer Institute. Juno Therapeutics has an exclusive
license to the St. Jude Childrens Research Hospital patented technology
for CD19-directed product candidates that use 4-1BB, which was developed
by Dario Campana, Chihaya Imai, and St. Jude Childrens Research
Hospital. Junos product candidate JCAR017 was developed in
collaboration with SCRI and others.

About the Juno-Celgene Collaboration

Celgene Corporation and Juno Therapeutics formed a collaboration in June
2015 under which the two companies will leverage T cell therapeutic
strategies to develop treatments for patients with cancer and autoimmune
diseases with an initial focus on chimeric antigen receptor (CAR) and T
cell receptor (TCR) technologies. In April 2016, Celgene exercised its
option to develop and commercialize the Juno CD19 program outside North
America and China.

Forward-Looking Statements

This press release contains "forward-looking statements" within the
meaning of the Private Securities Litigation Reform Act of 1995, Section
27A of the Securities Act of 1933, and Section 21E of the Securities
Exchange Act of 1934, including statements regarding Junos mission,
progress, and business plans; Junos participation at ASH and SITC and
the content of ASH and SITC presentations; clinical trial plans and
timelines; timing of regulatory submissions and approvals; the potential
best-in-class profile for JCAR017 and the potential for outpatient
administration; the potential of the Celgene collaboration; and 2017
cash burn forecast. Forward-looking statements are subject to risks and
uncertainties that could cause actual results to differ materially from
such forward-looking statements, and reported results should not be
considered as an indication of future performance. These risks and
uncertainties include, but are not limited to, risks associated with:
the success, cost, and timing of Junos product development activities
and clinical trials; Junos ability to obtain regulatory approval for
and to commercialize its product candidates; with respect to the timing
of JCAR017 approval, the time it takes to complete enrollment of the
pivotal cohort, the timing of Junos FDA submission, and the duration of
FDA review; Junos ability to establish a commercially-viable
manufacturing process and manufacturing infrastructure; regulatory
requirements and regulatory developments; success of Junos competitors
with respect to competing treatments and technologies; Junos dependence
on third-party collaborators and other contractors in Junos research
and development activities, including for the conduct of clinical trials
and the manufacture of Junos product candidates; Junos dependence on
Celgene for the development and commercialization outside of North
America and China of Junos CD19 product candidates and any other
product candidates for which Celgene exercises an option; Junos
dependence on JW Therapeutics (Shanghai) Co., Ltd, over which Juno does
not exercise complete control, for the development and commercialization
of product candidates in China; Junos ability to obtain, maintain, or
protect intellectual property rights related to its product candidates;
amongst others. For a further description of the risks and uncertainties
that could cause actual results to differ from those expressed in these
forward-looking statements, as well as risks relating to Junos business
in general, see the information Juno has included in its periodic
reports and other documents filed with the Securities and Exchange
Commission. These forward-looking statements speak only as of the date
hereof. Juno disclaims any obligation to update these forward-looking
statements.

To supplement the financial results presented in accordance with
generally accepted accounting principles in the United States (GAAP),
Juno uses certain non-GAAP financial measures to evaluate its business.
Junos management believes that these non-GAAP financial measures are
helpful in understanding Junos financial performance and potential
future results. These are not meant to be considered in isolation or as
a substitute for comparable GAAP measures and should be read in
conjunction with Junos financial statements prepared in accordance with
GAAP. These non-GAAP measures differ from GAAP measures with the same
captions, may be different from non-GAAP financial measures with the
same or similar captions that are used by other companies, and do not
reflect a comprehensive system of accounting. Junos management uses
these supplemental non-GAAP financial measures internally to understand,
manage, and evaluate Junos business and make operating decisions. In
addition, Junos management believes that the presentation of these
non-GAAP financial measures is useful to investors because they enhance
the ability of investors to compare Junos results from period to period
and allows for greater transparency with respect to key financial
metrics Juno uses in making operating decisions. Juno endeavors to
compensate for the limitation of the non-GAAP measures presented by also
providing the most directly comparable GAAP measures and descriptions of
the reconciling items and adjustments to derive the non-GAAP measures.
The Company has not reconciled guidance for non-GAAP metrics to their
most directly comparable GAAP measures because such items that impact
these measures cannot be reasonably predicted.

The following is a reconciliation of GAAP to non-GAAP financial measures:

(1) The upfront payments related to the acquisition of technology in
2016 include payments made in connection with technology licensing and
the acquisition of RedoxTherapies.

(2) The tenant improvement allowance is related to the build-out of the
Companys new headquarters facility and was recorded in operating
activities on the condensed consolidated statements of cash flows under
GAAP.

(1) The success payment expense (gain) represents the change in the
estimated fair value of the success payment obligations and the
associated elapsed service period. As of September 30, 2017, the
estimated fair values of the success payment liabilities to FHCRC and
MSK on the condensed consolidated balance sheets, were approximately
$51.0 million and $33.6 million, respectively. If success payment
thresholds are met in the future, Juno may pay FHCRC and MSK the
applicable success payment in cash or publicly-traded equity at Junos
election. The success payment liabilities are subject to re-measurement
each reporting period and may fluctuate from quarter-to-quarter and
year-to-year, sometimes significantly, resulting in either an expense or
a gain depending on the trading price of Juno common stock, estimated
term, expected volatility, risk-free interest rate, estimated number and
timing of valuation measurement dates, and estimated indirect costs that
are creditable against the success payments to FHCRC and MSK.

(2) This relates to a restricted stock grant in 2013 to a former
co-founding director who became a consultant upon his departure from
Junos board of directors in 2014. Unlike other outstanding awards to
Junos employees, scientific founders, and continuing directors, the
value of this restricted stock award is subject to re-measurement each
reporting period as the award vests and may result in the associated
expense fluctuating from quarter-to-quarter and year-to-year, sometimes
significantly, based on changes in the trading price of Juno common
stock through the end of the vesting period.

(3) This is the change in the estimated fair value of the contingent
consideration liabilities recorded in connection with the Stage and
X-Body acquisitions.

(4) This relates to the intangible asset acquired as part of the AbVitro
acquisition.

(5) The upfront payments related to the acquisition of technology in
2016 include payments made in connection with technology licensing and
the acquisition of RedoxTherapies.